Furious residents have sparked a council investigation with claims that a high-school building extension has robbed them of their privacy.
Neighbours of Shirley High School fear its new two-storey sixth-form block, which overlooks their houses, will allow pupils a clear view into their gardens while blocking out residents' previously picturesque view.
They said they had been deprived of the chance to object to the extension, which opened to students this week, because it differs from plans approved by Croydon Council in April.
Jane Newman, 60, who lives next to the academy in Shirley Church Road, said: "They have put up a building which is not according to the planning permission they were given.
Neighbours say the school has spoiled their view
"It is oversized, has additional windows overlooking residential properties and 20 air conditioning units which run the whole length of our garden.
"Because the building is taller than it should be it means that when the windows are open you will be able to see the whole of my garden."
The building has been fitting with opaque glass windows to obscure pupils' view into nearby gardens, but residents believe their privacy will still be compromised when the windows are open.
Mrs Newman's husband Roy, 65, said: "If they had stuck to the original size we would have happily accepted it but they misrepresented the size. We'll have no privacy at all and 20 industrial-size air conditioning units will be very noisy.
"We used to be able to watch the sunset from our garden but now we've just got this block. We are so angry that our voices haven't been heard."
Reg Munden, 83, who has lived with his wife Pauline in Shirley Church Road for 40 years, said: "It is right back on my back garden, shutting out all the light.
"Our outlook now is just one massive wall of the school. It really is a nightmare."
The academy, working through outside agent Synergy Edwards, is to submit another planning application to the council retrospectively.
But there is little chance of the application being rejected as pupils are already using the building.
The building's windows are fitting with obscure glass to prevent a clear view into neighbouring gardens
Spring Park Residents' Association is to hold a meeting to discuss concerns.
Trevor Ashby, its chairman, said: "People can ask for retrospective approval and it is up to the council what they do but I think it is just disappointing that a school or developer should do something that is different from the plans without consulting first of all. I think that is a concern."
Croydon Council, which did not commission the extension as the school is an academy, confirmed it was looking into residents' concerns.
Shirley High School in Shirley Church Road
A council spokesman said: "There is an on-going planning investigation underway regarding Shirley High’s new sixth-form building.
"We are awaiting revised plans from the school and these will be assessed in the normal way with the opportunity for local residents to submit comments."
Keith Bowen, chair of the schools' governors, said: "Our advisers are in discussion with Croydon Council planning officers to resolve any outstanding issues concerning the implementation of our planning permission."
- Domestic abuse centre opened in Norbury in memory of teen murdered by her boyfriend
- Did you get the secondary school place you wanted? Hundreds didn't
- VIDEO: Sunlight hits mirror sparking destructive house fire in Shirley
- Who’s been stealing this week? 16 people convicted by the courts this week for thefts
- Pub staff and suppliers owed thousands after landlady and her daughter vanish